Heat exchanger

ABSTRACT

A heat exchanger comprising: a core portion including a plurality of tubes; a pair of header tanks communicating with the tubes; and a pair of inserts arranged substantially parallel to the length of the tubes, and in such a manner as to contact the core portion at the ends of the core portion to transfer the heat from the core portion, and having the ends thereof supported on the header tanks; wherein a stress absorber to absorb the stress generated along the length of each insert is formed in the insert; wherein the stress absorber is formed over each insert from the upstream side to the downstream side in the air flow; and wherein the stress absorber is arranged in such a manner that the most upstream end and the most downstream end thereof in the air flow are not superposed, one on the other, along the direction of air flow.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part application of Ser. No. 11/484,519 filed on Jul. 11, 2006, claiming priority of Japanese Patent Application Nos. 2006-281454 filed Oct. 16, 2006, 2006-157725 filed Jun. 6, 2006 and 2005-202807 filed Jul. 12, 2005.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a heat exchanger or, in particular, to a heat exchanger effectively applicable to a multiflow radiator for cooling the cooling water of the internal combustion engine of an automotive vehicle.

2. Description of the Related Art

The conventional multiflow radiator includes a core portion having a plurality of tubes,-a header tank communicating with the plurality of the tubes and an insert arranged at the end of the core portion for reinforcing the core portion. Also, the header tank is configured of a core plate coupled with the tubes and a tank body providing an internal space of the tank. The tubes and the insert are inserted in the head tank and coupled to the core plate. Under these conditions, the tubes are held by equal forces by the insert through the fins.

In this radiator, the temperature of the cooling water flowing in the tubes may undergo a change. The amount of thermal expansion is different between the tubes directly affected by the cooling water and the insert affected indirectly by the cooling water. The difference in the amount of thermal expansion between the tubes and the insert is liable to generate thermal stress due to thermal distortion at the root (coupling) between the core plate and the tubes adjacent to the insert. A repeated change in temperature and hence a repeated change in thermal stress poses the problem that the tubes in the neighborhood of the root may be broken.

To obviate this problem, an anti-thermal distortion structure has been proposed in which the thermal distortion is absorbed by cutting the longitudinal central portion of the insert (Japanese Unexamined Patent Publication No. 11-325783).

In another conventional anti-thermal distortion structure that has been proposed, an expansion having a substantially semicircular cross section is formed on the insert and adapted to be deformed to absorb the thermal distortion (Japanese Unexamined Patent Publication No. 11-237197).

In the anti-thermal distortion structure proposed in Japanese Unexamined Patent Publication No. 11-325783, however, the notch of the insert reduces the strength to hold the tubes. In the case where the internal pressure in the tubes increases and the tubes expand under the pressure of the cooling water, the notch of the insert is locally deformed due to the pressure in the tubes. As a result, the portion of the tube adjacent to the notch is deformed by expansion and may break.

The anti-thermal distortion structure proposed by Japanese Unexamined Patent Publication No. 11-237197 also poses a similar problem to Japanese Unexamined Patent Publication No. 11-325783 due to the fact that the tube holding strength of the expansion of the insert is reduced.

SUMMARY OF THE INVENTION

In view of this fact, the object of the present invention is to provide a heat exchanger in which the thermal distortion is reduced while, at the same time, the pressure resistance performance is secured.

In order to achieve the object described above, according to a first aspect of the invention, there is provided a heat exchanger comprising a core portion (4) including a plurality of tubes (2) with a heat medium flowing therein, a pair of header tanks (5) extending in a direction perpendicular to the length of the tubes (2) at the longitudinal ends of the tubes (2) and communicating with the tubes (2), and a pair of inserts (6) arranged substantially parallel to the length of the tubes (2) in such a manner as to contact the core portion (4) at the ends of the core portion (4) and each having the ends thereof supported on the corresponding header tank (5), wherein, in order to absorb the stress generated along the length of each insert (6), a stress absorber (74, 76, 77) is formed over the distance from the upstream side to the downstream side of the insert (6) in the air flow in such a manner that the most upstream end and the most downstream end of the stress absorber (74, 76, 77) in the air flow are not superposed, one on the other, along the direction of air flow.

By forming the stress absorber (74, 76, 77) in the insert (7) as described above, the stress generated along the length of the insert (7) can be absorbed. Also, in view of the fact that the stress absorber (74, 76, 77) is formed with the most upstream and the most downstream ends thereof in the air flow not superposed one on the other along the direction of air flow, the stress absorber (74, 76, 77), i.e. the portion of the insert (7) having a weak force to hold the tubes (2) can be dispersed over the length of the tubes (2). In the case where the internal pressure of the tubes (2) increases, therefore, the insert (7) is prevented from being deformed locally by the stress absorber (74, 76, 77). In this way, the tubes (2) are prevented from being broken by expansion and deformation. As a result, the thermal distortion can be reduced while at the same time the pressure resistance performance is secured.

Each tube (2) may have a flat cross section in the direction of air flow, and the insert (7) may include a base portion (71) having a surface substantially parallel to the flat surface (2a) of the tube (2) and extending substantially in parallel to the length of the tube (2), and ribs (72) projected in a direction substantially perpendicular to the base portion (71) from the ends of the base portion (71) in the direction of air flow and are extended substantially parallel to the length of the tube (2), wherein the portions of the ribs (72) corresponding to the most upstream and the most downstream ends of the stress absorber are formed with notches (73 a, 73 b), respectively, and the stress absorber constitutes a base portion-side expansion (74) having a substantially U-shaped cross section of the base portion (71).

A “substantial U shape” is a shape configured of two substantially opposed parallel surfaces and a substantially arcuate bottom surface connected to the two surfaces, in which the bottom surface may include a horizontal portion. In other words, the cross section may be substantially channel-shaped.

In this case, the base portion-side expansion (74) may be tilted with respect to the direction of air flow.

According to a second aspect of the invention, there is provided a heat exchanger wherein the base portion-side expansion (74) is split into a plurality of portions in the direction of air flow, which are connected to each other through slits (75) formed in the cross section of the base portion (71).

As a result, the length of the base portion-side expansion (74) along the direction of air flow can be reduced by the length of the slits (75) in the direction of air flow, thereby improving the moldability.

According to a third aspect of the invention, there is provided a heat exchanger wherein a plurality of the base portion-side expansions (74) are not aligned.

As a result, the distance between the notch (73 a) on the upstream side in the air flow and the notch (73 b) on the downstream side in the air flow can be increased without increasing the angle that the base portion-side expansion (74) forms with the direction of air flow. Thus, the pressure resistance performance can be positively secured without deteriorating the moldability of the base portion-side expansion (74).

According to a fourth aspect of the invention, there is provided a heat exchanger wherein the plurality of the base portion-side expansions (74) are tilted in different directions from the direction of air flow.

This configuration can reduce the spring back at the time of molding the plurality of the base portion-side expansions (74) and thus improve the moldability.

According to a fifth aspect of the invention, there is provided a heat exchanger wherein the plurality of the base portion-side expansions (74) are arranged substantially parallel to the direction of air flow in such a manner as not be superposed one on another in the direction of air flow.

This configuration eliminates the need of tilting the base portion-side expansions (74) from the direction of air flow and therefore the moldability can be improved.

According to a sixth aspect of the invention, there is provided a heat exchanger wherein each tube (2) has a flat cross section in the direction of air flow and the insert (7) includes a base portion (71) having a surface substantially parallel to the flat surface (2 a) of the tube (2) and extending in the direction substantially parallel to the length of the tube (2) and ribs (72) projected in the direction substantially perpendicular to the base portion (71) and extending in the direction substantially parallel to the length of the tube (2), and wherein the stress absorber is a notch (76), cut in the base portion (71), diagonal to the direction of air flow.

As a result, the stress absorber can be configured of only the notch (76) formed in the insert (7), and therefore the pressure resistance performance can be secured with a simple configuration.

According to a seventh aspect of the invention, there is provided a heat exchanger wherein only one end of the notch (76) is open.

This configuration leaves one of the ribs (72) intact and can avoid reducing a rigidity more than requires. As a result, the force to hold the tubes (2) can be increased. Thus, the thermal distortion can be reduced while, at the same time, positively securing the pressure resistance performance.

Alternatively, the two ends of the notch (76) may be open or connected to each other.

Further, a plurality of the notches (76) may be formed.

Furthermore, only one end of each of a plurality of notches (76) may be open, and the open ends of the plurality of the notches (76) may be arranged alternately between the upstream side and the downstream side of the base portion (71) in the air flow.

In addition, the plurality of the notches (76) can be tilted in directions different from the direction of air flow.

According to an eighth aspect of the invention, there is provided a heat exchanger wherein the notch (76) is formed in the base portion (71), the portion of the pair of the ribs (72) adjoining the notch (76) is formed with a U-shaped rib-side expansion (77) in the direction of air flow, and the stress absorber includes the rib-side expansion (77).

By forming at least a notch (76) in the base portion (71) and the rib-side expansions (77) on a pair of the ribs (72) in this way, the stress generated along the length of each insert can be positively absorbed.

According to a ninth aspect of the invention, the insert (7) is formed with protrusions (78) projected outward along the direction in which the tubes (2) are stacked and connected to a stress absorber (74, 76, 77).

Upon application of a pressure (when the internal pressure of the tubes (2) increases), the whole heat exchanger (1) is deformed to expand along the direction in which the tubes (2) are stacked, and upon vibration, the whole heat exchanger (1) is deformed along both the length of the tubes (2) and the direction in which the tubes (2) are stacked. The provision of the protrusions (78) of the insert (7) projected outward along the direction in which the tubes (2) are stacked, however, makes it possible to increase the stiffness of the insert (7) along the direction in which the tubes (2) are stacked. As a result, the pressure resistance and the earthquake resistance are improved.

According to a tenth aspect of the invention, the tubes (2) have a flat section along the direction of air flow, the insert (7) includes a base portion (71) having a surface substantially parallel to the flat surface of the tubes (2) and extending in the direction substantially parallel to the length of the tubes (2), the base portion (71) has base portion-side ribs (78) projected outward along the direction in which the tubes (2) are stacked and extending in the direction substantially parallel to the length of the insert (7), the stress absorbing portion is a base portion-side expansion (74) of the base portion (71) having the section expanded substantially in the shape of U, and an end of each of the base portion-side ribs (78) is connected to the base portion-side expansion (74).

As described above, in view of the fact that the base portion (71) of the insert (7) is formed with the base portion-side ribs (78) projected outward along the direction in which the tubes (2) are stacked, the stiffness of the insert (7) in the direction along which the tubes (2) are stacked can be improved, thereby improving the pressure resistance and the earthquake resistance.

The stress, if generated along the length of the insert (7), may be concentrated at the connector between the base portion (71) of the insert (7) and the base portion-side expansion (74) and may damage the connector. By connecting an end of each of the base portion-side ribs (78) to the base portion-side expansion (74), however, the stress is prevented from being concentrated on the connector between the base portion (71) and the base portion-side expansion (74).

According to an eleventh aspect of the invention, the insert (7) has a pair of side ribs (72) projected in the direction substantially perpendicular to the base portion (71) from the ends of the base portion (71) along the direction of air flow, and the parts of the side ribs (72) corresponding to the most upstream end and the most downstream end of the base portion-side expansion (74) are formed with notches (73 a, 73 b).

In view of the fact that the base portion (71) of the insert (7) is formed with the base portion-side ribs (78) projected outward along the direction in which the tubes (2) are stacked as described above, the stiffness of the insert (7) along the direction in which the tubes (2) are stacked can be improved. As a result, even in the case where the height (length along the direction in which the tubes (2) are stacked) of the side ribs (72) is reduced, the stiffness of the insert (7), i.e. the strength of the heat exchanger (1) can be secured. Even in the case where the mounting space of the heat exchanger (1) is limited, therefore, the height (length along the direction in which the tubes (2) are stacked) of the core portion (4) can be increased by the amount corresponding to the height reduction of the side ribs (72), and therefore, the heat exchange performance is improved.

According to a twelfth aspect of the invention, the base portion-side ribs (78) are arranged in a pair on both sides, respectively, of the base portion-side expansion (74).

As a result, the base portion-side ribs (78) can be arranged over a wide range along the length of the insert (7). Thus, the stiffness of the insert (7) along the direction in which the tubes (2) are stacked can be further increased for a further increased pressure resistance and earthquake resistance.

In the twelfth aspect described above, the base portion-side ribs (78) can be arranged on one and the other sides, respectively, of the center line (L) of the base portion (71) along the direction of air flow across the length of the insert (7). As a result, the base portion-side ribs (78) can be arranged over a wide range of the insert (7) in the direction of the air flow, and therefore, the stiffness of the insert (7) along the direction in which the tubes (2) are stacked can be further increased. Thus, the pressure resistance and the earthquake resistance are further improved.

According to a thirteenth aspect of the invention, the base portion (71) is formed with second base portion-side ribs (78 a) projected outward along the direction in which the tubes (2) are stacked and extending substantially in parallel to the length of the insert (7). This makes it possible to increase the stiffness of the insert (7) along the direction in which the tubes (2) are stacked for an improved pressure resistance and an improved earthquake resistance.

According to a fourteenth aspect of the invention, the base portion-side ribs (78) are arranged on one and the other sides, respectively, of the center line (L) of the base portion (71) along the direction of air flow across the length of the insert (7), the base portion (71) has second base portion-side ribs (78 a) projected outward along the direction in which the tubes (2) are stacked and extending substantially in parallel to the length of the insert (7), the second base portion-side ribs (78 a) are each arranged on one of the two sides of the base portion-side expansion (74), i.e. on one and the other sides, respectively, of the center line (L) of the base portion (71) along the direction of air flow across the length of the insert (7), and the second base portion-side ribs (78 a) are arranged in opposed relation to the base portion-side ribs (78) with respect to the base portion-side expansion (74) on one and the other sides, respectively, of the center line (L).

As a result, the stiffness of the insert (7) along the direction in which the tubes (2) are stacked can be further increased for an improved resistance to pressure and earthquake.

In the fourteenth aspect described above, an end of each of the second base portion-side ribs (78 a) can be connected to the base portion-side expansion (74). As a result, the stress concentration on the connector between the base portion (71) and the base portion-side expansion (74) can be more positively prevented.

Also, the base portion-side ribs (78) are each arranged, on one of the sides of the base portion-side expansion (74) and aligned with each other, the base portion (71) is formed with second base portion-side ribs (78 a) projected along the direction in which the tubes (2) are stacked and extending substantially in parallel to the length of the insert (7), and the second base portion-side ribs (78) are each arranged on one of the two sides of the base portion-side expansion (74) and connected to the base portion-side ribs (78), respectively.

According to a fifteenth aspect of the invention, a notch (76) is extended to the side ribs (72), the ends of the notch (76) are arranged in the planes of a pair of the side ribs (72), the insert (7) is formed with second notches (79) substantially parallel to the notch (76) from the outer end of the side ribs (72) along the direction in which the tubes (2) are stacked, and only one end of each of the second notches (79) is open.

As a result, the side ribs (72) of the insert (7) are not fully cut, and therefore, the stiffness of the insert (7) is prevented from being unnecessarily decreased, thereby making it possible to positively increase both the pressure resistance and the quake resistance.

Further, the notch (76) and the second notches (79) are formed before press forming the insert (7), and therefore, the formability is improved.

In the present specification, the expression “substantially parallel” or “substantially in parallel” should be interpreted not necessarily to mean “completely parallel” or “completely in parallel” but may be interpreted to mean “almost parallel” or “almost in parallel”.

Incidentally, the reference numerals in parentheses, to denote the above means, are intended to show the relationships between the specific means which will be described later in an embodiment of the invention.

The present invention may be more fully understood from the description of preferred embodiments of the invention, as set forth below, together with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of the radiator 1 according to a first embodiment.

FIG. 2A is a plan view showing the insert 7 according to the first embodiment.

FIG. 2B is a front view of FIG. 2.A.

FIG. 3A is a plan view showing the insert 7 according to a second embodiment.

FIG. 3B is a front view of FIG. 3A.

FIG. 4A is a plan view showing the insert 7 according to a third embodiment.

FIG. 4B is a front view of FIG. 4A.

FIG. 5A is a plan view showing the insert 7 according to a fourth embodiment.

FIG. 5B is a front view of FIG. 5A.

FIG. 6A is a plan view showing the insert 7 according to a fifth embodiment.

FIG. 6B is a front view of FIG. 6A.

FIG. 7A is a plan view showing the insert 7 according to a sixth embodiment.

FIG. 7B is a front view of FIG. 7A.

FIG. 8A is a plan view showing the insert 7 according to a seventh embodiment.

FIG. 8B is a front view of FIG. 8A.

FIG. 9A is a plan view showing the insert 7 according to an eighth embodiment.

FIG. 9B is a front view of FIG. 9A.

FIG. 10A is a plan view showing the insert 7 according to a ninth embodiment.

FIG. 10B is a front view of FIG. 10A.

FIG. 11A is a plan view showing the insert 7 according to a tenth embodiment.

FIG. 11B is a front view of FIG. 11A.

FIG. 12 is a perspective view showing the insert 7 according to the tenth embodiment.

FIG. 13 is a perspective view showing the insert 7 according to an eleventh embodiment.

FIG. 14A is a view taken along arrow A in FIG. 13.

FIG. 14B is a sectional view taken along line B-B in FIG. 13.

FIG. 14C is a sectional view taken along line C-C in FIG. 13.

FIG. 15 is a perspective view showing the insert 7 according to a twelfth embodiment.

FIG. 16A is a view taken along arrow D in FIG. 15.

FIG. 16B is a sectional view taken along line E-E in FIG. 15.

FIG. 16C is a sectional view taken along line F-F in FIG. 15.

FIG. 17 is a perspective view showing the insert 7 according to a thirteenth embodiment.

FIG. 18 is a perspective view showing the insert 7 according to a fourteenth embodiment.

FIG. 19 is a perspective view showing the insert 7 according to a fifteenth embodiment.

FIG. 20 is a perspective view showing the insert 7 according to a sixteenth embodiment.

FIG. 21 is a perspective view showing the insert 7 according to a seventeenth embodiment.

FIG. 22 is a perspective view showing the insert 7 according to an eighteenth embodiment.

FIG. 23 is a perspective view showing the insert 7 according to a nineteenth embodiment.

FIG. 24 is a plan view schematically showing the insert 7 before bending the side ribs 72 according to the nineteenth embodiment.

FIG. 25 is a perspective view showing the insert 7 according to a twentieth embodiment.

FIG. 26 is a perspective view showing the insert 7 according to a twenty-first embodiment.

FIG. 27 is a perspective view showing the insert 7 according to a twenty-second embodiment.

DESCRIPTION OF PREFERRED EMBODIMENTS

The first embodiment of the invention is explained below with reference to FIGS. 1, 2. This embodiment is an application of the heat exchanger according to this invention to the radiator 1 for exchanging heat between the air and the cooling water (heat medium) that has cooled the vehicle engine. FIG. 1 is a front view of the radiator 1 according to the first embodiment.

In FIG. 1, the cooling water flows in the tubes 2. Each tube 2 is flat so that the direction of air flow (direction perpendicular to the page) coincides with the direction of the long diameter, and a plurality of the tubes 2 are arranged in parallel to each other in vertical direction in such a manner that the longitudinal direction thereof coincides with the horizontal direction.

The flat surfaces on the two sides of each tube 2 are coupled with the corrugated fins 3, whereby the heat transfer area with the air is increased to promote the heat exchange between the cooling water and the air. The substantially rectangular heat exchange unit including the tubes 2 and the fins 3 is hereinafter referred to as the core portion 4.

The header tank 5 extends in the direction (vertical direction in this embodiment) perpendicular to the length of the tubes 2 at each longitudinal end (horizontal ends in this embodiment) of the tubes 2 and communicates with a plurality of the tubes 2. The header tank 5 includes a core plate 5 a coupled with the tubes 2 inserted therein and a tank body 5 b providing the internal space of the tank with the core plate 5 a.

The header tank 5 includes a cooling water inlet 6 a connected to the cooling water outlet side of the engine (not shown) and a cooling water outlet 6 b connected to the cooling water inlet side of the engine. Also, an insert 7 for reinforcing the core portion 4 extends in the direction substantially parallel to the length of the tubes 2 at each end of the core portion 4.

FIG. 2A is a plan view showing the insert 7 according to the first embodiment, and FIG. 2B a front view of FIG. 2A. As shown in FIGS. 2A, 2B, the insert 7 includes a base portion 71 having a surface substantially parallel to the flat surface 2 a of the tubes 2 and extending in the direction substantially in parallel to the length of the tubes 2 and a pair of ribs 72 projected from the ends of the base portion 71 along the air flow in the direction (direction of tube stack) substantially perpendicular to the base portion 71 and extending in a direction substantially parallel to the length of the tubes 2.

The pair of the ribs 72 of the insert 7 are formed with notches 73 a, 73 b, respectively, cut inward in the direction of the tube stack from the outer end of the ribs 72 in the direction of the tube stack. Also, the notch (hereinafter referred to the upstream side notch 73 a) formed in the rib 72 on the upstream side in the air flow and the notch (hereinafter referred to as the downstream side notch 73 b) formed in the rib 72 on the downstream side in the air flow are arranged in such a manner as not be superposed, one on the other, in the direction of air flow.

The base portion 71 of the insert 7 is formed with a base portion-side expansion 74. The base portion-side expansion 74 is formed by expanding the cross section of the base portion 71 substantially into a U shape in the direction of the tube stack. Also, the base portion-side expansion 74 is so configured to be deformed to absorb the tension or compression stress generated along the length of the insert 7.

As shown in FIG. 2A, the base portion-side expansion 74 is formed to connect the upstream-side notch 73 a and the downstream-side notch 73 b and is arranged diagonally to the direction of air flow.

As explained above, the base portion 71 of the inset 6 is formed with the base portion-side expansion 74 having a substantially U-shaped cross section, and therefore the stress generated along the length of the insert can be absorbed.

Also, by arranging the base portion-side expansion 74 diagonally to the direction of air flow, the stress absorber of the insert 7, i.e. the portion of the insert 7 weak in the force to hold the tube 2 can be dispersed over the length of the tube. As a result, in the case where the internal pressure of the tube 2 increases, the base portion-side expansion 74 of the insert 7 can be prevented from being locally deformed. Thus, the tube 2 is prevented from being deformed by expansion thereby preventing the breakage of the tube 2.

Thus, the thermal distortion is reduced and the pressure resistance performance is secured at the same time.

Next, a second embodiment of the invention will be explained with reference to FIGS. 3A, 3B. In FIGS. 3A, 3B, component parts similar or identical to those of the first embodiment are designated by the same reference numerals, respectively, and are not described again. FIG. 3A is a plan view showing the insert 7 according to the second embodiment, and FIG. 3B a front view of FIG. 3A.

As shown in FIGS. 3A, 3B, the base portion 71 of the insert 7 according to this embodiment is formed with a slit 75. According to this embodiment, the slit 75 is arranged with the length thereof substantially parallel to the length of the tubes 2.

Also, the base portion-side expansion 74 is split into two parts in the direction of air flow. Of the two base portion-side expansions 74 thus split, the one arranged upstream in the air flow is called a first base portion-side expansion 74 a and the one arranged downstream in the air flow a second base portion-side expansion 74 b.

The two base portion-side expansions 74 a, 74 b are connected to each other through the slit 75. Also, the two base portion-side expansions 74 a, 74 b are arranged out of alignment. According to this embodiment, the two base portion-side expansions 74 a, 74 b are connected to the longitudinal ends, respectively, of the slit 75.

As a result, effects similar to those of the first embodiment are produced.

Further, in view of the fact that the base portion-side expansion 74 is split into two parts in the direction of air flow and the two base portion-side expansions 74 a, 74 b thus split are connected to each other through the slit 75, the length of the base portion-side expansion 74 can be reduced by the length of the slit 75 in the direction of air flow. As a result, the moldability is improved.

Also, in view of the fact that the two base portion-side expansions 74 a, 74 b are not arranged in alignment, the distance between the upstream-side notch 73 a and the downstream-side notch 73 b in the air flow can be increased without changing the angle of the base portion-side expansion 74 with respect to the direction of air flow. As a result, the pressure resistance performance can be positively secured without reducing the moldability of the base portion-side expansion 74.

Next, a third embodiment of the invention will be explained with reference to FIGS. 4A, 4B. In FIGS. 4A, 4B, component parts similar or identical to those of the second embodiment are designated by the same reference numerals, respectively, and not described again. FIG. 4A is a plan view showing the insert 7 according to the tenth embodiment, and FIG. 4B a front view of FIG. 4A.

As shown in FIG. 4A, the two base portion-side expansions 74 a, 74 b according to this embodiment are tilted in opposite directions with respect to the direction of air flow.

More specifically, the end of the slit 75 connected with the first base portion-side expansion 74 a is arranged nearer to the downstream-side notch 73 b than to the upstream-side notch 73 a in the direction of the length of the tube. The end of the slit 75 connected with the second base portion-side expansion 74 b, on the other hand, is arranged farther from the upstream-side notch 73 a than from the downstream-side notch 73 b in the direction along the length of the tube.

As a result, effects similar to those of the second embodiment are produced.

Further, in view of the fact that the two base portion-side expansions 74 a, 74 b are tilted in opposite directions in the direction of air flow, the spring back when molding the base portion-side expansions 74 a, 74 b can be reduced for an improved moldability.

Next, a fourth embodiment of the invention will be explained with reference to FIGS. 5A, 5B. In FIGS. 5A, 5B, component parts similar or identical to those of the second embodiment are designated by the same reference numerals, respectively, and are not described again. FIG. 5A is a plan view showing the insert 7 according to the fourth embodiment, and FIG. 5B is a front view of FIG. 5A.

As shown in FIGS. 5A, 5B, the base portion 71 of the insert 7 according to this embodiment is formed with two slits 75. According to this embodiment, the two slits 75 are arranged with the length thereof substantially parallel to the length of the tubes. Of the two slits 75, the one arranged on the upstream side in the air flow is called a first slit 75 a and the one arranged downstream side in the air flow a second slit 75 b.

The base portion-side expansion 74 is split into three parts in the direction along the air flow. The resultant three base portion-side expansions 74 a to 74 c are arranged substantially parallel to the direction of air flow in such a manner as not to be superposed, one on another, in the direction of air flow. Of the three base portion-side expansions 74, the one arranged upstream in the air flow is called a first base portion-side expansion unit 74 a, the one arranged downstream in the air flow a second base portion-side expansion 74 b, and the one arranged between the first base portion-side expansion 74 a and the second base portion-side expansion 74 c a third base portion-side expansion 74 c.

As shown in FIG. 5A, the three base portion-side expansions 74 a to 74 c are coupled to each other through the two slits 75 a, 75 b. More specifically, one end of the first slit 75 a along the tube length is connected to the first base portion-side expansion 74 a, and the other end thereof to the third base portion-side expansion 74 c. The downstream end of the third base portion-side expansion 74 c along the direction of air flow is connected to one end of the second slit 75 b along the tube length, and the other end thereof to the second base portion-side expansion 74 b.

As a result, effects similar to those of the second embodiment are produced.

Further, in view of the fact that the three base portion-side expansions 74 a to 74 c are formed substantially in parallel to the direction of air flow in such a manner as not to be superposed, one on another, in the direction of air flow, the base portion-side expansion 74 is not required to be tilted from the direction of air flow, and therefore the moldability is improved.

Next, a fifth embodiment of the invention will be explained with reference to FIGS. 6A and 6B. In FIGS. 6A and 6B, the component parts similar or identical to those of the first embodiment are designated by the same reference numerals, respectively, and not described any more. FIG. 6A is a plan view showing the insert 7 according to the fifth embodiment, and FIG. 6B is a front view of FIG. 6A.

As shown in FIGS. 6A and 6B, the insert 7 according to this embodiment is formed with a notch 76. The notch 76 is formed by cutting the base portion 71 diagonally from one end to the other end in the direction of air flow in such a manner as to be tilted from the direction of air flow. As a result, the upstream and downstream ends of the notch 76 in the air flow are prevented from being superposed, one on the other, in the direction of air flow.

According to this embodiment, the notch 76 is formed continuously from the upstream end to the downstream end of the base portion 71 in the air flow. Also, the notch 76 is formed continuously in the ribs 72. More specifically, the portion of each rib 72 adjacent to the end of the notch 76 is notched substantially in parallel to the direction along the tube stack. According to this embodiment, therefore, the insert 7 is completely separated by the notch 76.

As described above, by forming the notch 76 in the base portion 71 of the insert 7, the stress generated along the length of the insert 7 can be absorbed.

Also, in view of the fact that the notch 76 is arranged diagonally with respect to the direction of air flow, the stress absorber of the insert 7, i.e. the portion of the insert 7 having little strength to hold the tube 2 can be dispersed along the tube length. In the case where the internal pressure of the tube 2 increases, therefore, the tube 2 is prevented from being locally deformed by expansion, thereby making it possible to prevent the tube 2 being broken.

Thus, the thermal distortion can be reduced while, at the same time, the pressure resistance performance is secured.

Further, in view of the fact that the stress generated along the length of the insert 7 can be absorbed simply by forming the notch 76 in the insert 7, the pressure resistance performance can be secured with a simple configuration.

Next, a sixteenth embodiment of the invention will be explained with reference to FIGS. 7A and 7B. In FIGS. 7A and 7B, component parts similar or identical to those of the fifth embodiment are designated by the same reference numerals, respectively, and are not described again. FIG. 7A is a plan view showing the insert 7 according to the sixth embodiment, and FIG. 7B a front view of FIG. 7A.

As shown in FIGS. 7A and 7B, only one end (the upstream end in the air flow in this embodiment) of the notch 76 according to this embodiment is open. More specifically, one end of the notch 76 in the direction of air flow is connected to an end of the base portion 71 in the direction of air flow, and the other end (the downstream end in the air flow in this embodiment) of the notch 76 is located within the base portion 71. In other words, according to this embodiment, the insert 7 is not completely separated by the notch 76.

As described above, by opening only one end of this notch 76, one rib 72 is left intact and, therefore, an undesired rigidity reduction can be avoided. As a result, the force to hold the tubes 2 can be increased, thereby reducing the thermal distortion while, at the same time, positively securing the pressure resistance performance.

Next, a seventh embodiment of the invention will be explained with reference to FIGS. 8A and 8B. In FIGS. 8A and 8B, component parts similar or identical to those of the sixth embodiment are designated by the same reference numerals, respectively, and are not described again. FIG. 8A is a plan view showing the insert 7 according to the seventh embodiment, and FIG. 8B a front view of FIG. 8A.

As shown in FIGS. 8A and 8B, the base portion 71 of the insert 7 according to this embodiment is formed with three parallel notches 76. The three notches 76 are all formed by cutting the base portion 71, from the upstream end toward the downstream end thereof in the air flow.

By forming the three notches 76 in the base portion 71 in this way, the stress generated in the direction along the length of the insert 7 can be positively absorbed. Thus, the thermal distortion can be reduced while, at the same time, the pressure resistance performance is secured.

Next, an eighth embodiment of the invention will be explained with reference to FIGS. 9A and 9B. In FIGS. 9A and 9B, component parts similar or identical to those of the seventh embodiment are designated by the same reference numerals, respectively, and are not described again. FIG. 9A is a plan view showing the insert 7 according to the eighth embodiment, and FIG. 9B is a front view of FIG. 9A.

As shown in FIGS. 9A and 9B, the base portion 71 of the insert 7 is formed with three parallel notches 76. According to this embodiment, the notch 76 a arranged outside and along the tube length is formed by cutting the base portion 71, from the upstream end toward the downstream end in the air flow. The notch 76 b arranged inside in the direction of tube stack, on the other hand, is formed by cutting the base portion 71 from the downstream end to the upstream end in the air flow.

As a result, effects similar to those of the seventh embodiment described above are achieved.

Next, a ninth embodiment of the invention will be explained with reference to FIGS. 10A and 10B. In FIGS. 10A and 10B, component parts similar or identical to those of the seventh embodiment are designated by the same reference numerals, respectively, and are not described again. FIG. 10A is a plan view showing the insert 7 according to the ninth embodiment, and FIG. 10B a front view of FIG. 10A.

As shown in FIGS. 10A and 10B, the base portion 71 of the insert 7 according to this embodiment is formed with four notches 76. Of the four notches 76, two (hereinafter referred to as first notch portions 76 c) are formed by cutting the base portion 71, from the upstream end toward the downstream end in the air flow. The two other notches (hereinafter referred to as a second notch portion 76 d), other than the first notch portion 76 c, on the other hand, are formed by cutting the base portion 71, from the downstream end toward the upstream end in the air flow.

The two notches of the first notch portion 76 c are arranged substantially parallel to each other. The two notches of the second notch portion 76 d, on the other hand, are tilted in the opposite direction to the first notch portion 76 c in the direction of air flow. Also, the two notches of the second notch portion 76 d are arranged substantially in parallel to each other.

As a result, effects similar to those of the seventh embodiment described above are produced.

Next, a tenth embodiment of the invention will be explained with reference to FIGS. 11A, 11B. In FIGS. 11A, 11B, component parts similar or identical to those of the fifth embodiment are designated by the same reference numerals, respectively, and are not described again. FIG. 11A is a plan view showing the insert 7 according to the tenth embodiment, and FIG. 11B a front view of FIG. 11A. FIG. 12 is a perspective view showing the insert 7 according to the tenth embodiment.

As shown in FIGS. 11A, 11B and 12, the ends of the notch 76 (hereinafter referred to as the rectangular portions 760) in the direction of air flow according to this embodiment are substantially rectangular and larger than the other parts of the notch 76. Also, the portion of each rib 72 adjacent to the corresponding rectangular portion 760 is formed with a rib-side expansion 77 of the rib 72 having a substantially U-shaped cross section. According to this embodiment, the rib-side expansions 77 are formed inward of the insert 7 in the direction of air flow.

As described above, by forming the notch 76 in the base portion 71 and the rib-side expansions 77 of the pair of the ribs 72, the stress generated in the direction along the length of the insert can be positively absorbed.

Also, the diagonal arrangement of the notch 76, with respect to the direction of air flow, makes it possible to disperse the stress absorber of the insert 7, i.e. the portion of the insert 7 having a weak force to hold the tubes 2, over the length of the tube. As a result, in the case where the internal pressure of the tube 2 increases, the tube 2 is prevented from being locally expanded and deformed, thereby making it possible to prevent the tube 2 from being broken.

As a result, thermal distortion is positively reduced while at the same time the pressure resistance performance is secured.

Next, the eleventh embodiment of the invention is explained with reference to FIGS. 13 and 14. The component parts similar to those of the first embodiment described above are designated by the same reference numerals, respectively, and not explained again.

FIG. 13 is a perspective view showing the insert 7 according to the eleventh embodiment, FIG. 14A is a view taken along arrow A in FIG. 13, FIG. 14B is a sectional view taken in line B-B in FIG. 13, and FIG. 14C is a sectional view taken in line C-C in FIG. 13.

As shown in FIGS. 13 and 14A to 14C, the base portion 71 of the insert 7 is formed with base portion-side ribs (protrusions) 78 projected outward along the direction in which the tubes 2 are stacked and extending substantially parallel to the length of the insert 7. The base portion-side ribs 78 have an end thereof connected to the base portion-side expansion 74. According to this embodiment, the other end of each of the base portion-side ribs 78 is arranged at the longitudinal ends of the base portion 71.

The base portion-side ribs 78 are each arranged on each side of the base portion-side expansion 74, or specifically, one each on each of the sides of the base portion-side expansion 74 on the base portion 71. The two base portion-side ribs 78 are arranged on one and the other sides, respectively, of the center line L across the length of the insert 7 (hereinafter referred to simply as the center line) of the base portion 71 in the direction of air flow. According to this embodiment, the two base portion-side ribs 78 are connected to one and the other ends, respectively, of the base portion-side expansion 74 in the direction of air flow.

Also, as shown in FIGS. 14B and 14C, the base portion-side ribs 78 are formed to have a substantially semicircular section.

Upon application of pressure thereto (when the internal pressure of the tubes 2 rises), the whole radiator 1 is deformed to expand along the direction in which the tubes 2 are stacked, and upon vehicle vibration, the whole radiator 1 is deformed both along the length of the tubes 2 and along the direction in which the tubes 2 are stacked. By forming the base portion-side expansion 74 with the section thereof expanded substantially in the shape of U on the base portion 71 of the insert 7, on the other hand, the stress generated along the length of the insert 7 can be absorbed. Further, according to this embodiment, the base portion-side ribs 78 projected outward along the direction in which the tubes 2 are stacked are formed on the base portion 71 of the insert 7, so that the stiffness of the insert 7 along the direction in which the tubes 2 are stacked can be improved. As a result, the resistance to both the pressure and the earthquake is improved.

The stress, if generated along the length of the insert 7, is concentrated at the connector between the base portion 71 of the insert 7 and the base portion-side expansion 74 and may break the connector. By connecting one end of each of the base portion-side ribs 78 to the base portion-side expansion 74, on the other hand, the stress concentration at the connector between the base portion 71 and the base portion-side expansion 74 is prevented.

Also, the stiffness of the insert 7 along the direction in which the tubes 2.are stacked can be secured by the base portion-side ribs 78, and therefore, the height of the side ribs 72 (the length along the direction in which the tubes 2 are stacked) can be reduced. Therefore, even in the case where the mounting space of the radiator 1 is limited, the core portion 4 can be enlarged by the amount corresponding to the height reduction of the side ribs 72, thereby making it possible to improve the heat exchange performance.

Also, one each of the base portion-side ribs 78 is arranged on each side of the base portion-side expansion 74, and therefore, the base portion-side ribs 78 can be arranged over a wide range in the longitudinal direction of the insert 7, thereby making it possible to further increase the stiffness of the insert 7 along the direction in which the tubes 2 are stacked. Thus, the pressure resistance and the quake resistance are improved.

Further, the base portion-side ribs 78 are arranged on one and the other sides of the center line L of the base portion 71, and therefore, the base portion-side ribs 78 can be arranged over a wide range on the insert 7 in the direction of air flow. Thus, the stiffness of the insert 7 along the direction in which the tubes 2 are stacked can be further increased. Thus, the pressure resistance and the quake resistance can be improved.

Next, the twelfth embodiment of the invention is explained with reference to FIGS. 15 and 16. The twelfth embodiment, compared with the eleventh embodiment described above, is different in that the side ribs 72 are omitted. The component parts similar to those of the eleventh embodiment are designated by the same reference numerals, respectively, and not explained.

FIG. 15 is a perspective view showing the insert 7 according to the twelfth embodiment. FIG. 16A is a view taken along arrow in FIG. 15, FIG. 16B is a sectional view taken in line E-E in FIG. 15, and FIG. 16C is a sectional view taken in line F-F in FIG. 15. As shown in FIGS. 15 and 16A to 16C, the insert 7 has only the base portion 71.

As described above, by providing the base portion 71 of the insert 7 with the base portion-side ribs 78 projected outward along the direction in which the tubes 2 are stacked, the stiffness of the insert 7 along the direction in which the tubes 2 are stacked can be increased, and therefore, the side ribs can be omitted. As a result, even in the case where the mounting space of the radiator 1 is limited, the core portion 4 can be increased in size by the amount corresponding to the side ribs removed. Thus, heat exchange performance is improved.

Next, the thirteenth embodiment of the invention is explained with reference to FIG. 17. The thirteenth embodiment is different from the twelfth embodiment in that the base portion-side ribs 78 are differently arranged. The component parts similar to those of the twelfth embodiment are designated by the same reference numerals, respectively, and not explained again.

FIG. 17 is a perspective view showing the insert 7 according to the thirteenth embodiment. As shown in FIG. 17, the two base portion-side ribs 78 arranged on the two sides, respectively, of the base portion-side expansion 74 of the base portion 71 are connected to the base portion-side expansion 74 in the neighborhood of the center of air flow. As a result, the effects similar to those of the twelfth embodiment are obtained.

Next, the fourteenth embodiment of the invention is explained with reference to FIG. 18. The fourteenth embodiment is different from the eleventh embodiment in that the base portion-side ribs 78 are differently arranged. The component parts similar to those of the eleventh embodiment are designated by the same reference numerals, respectively, and not explained more.

FIG. 18 is a perspective view showing the insert 7 according to the fourteenth embodiment. As shown in FIG. 18, the two base portion-side ribs 78 arranged on both sides of the base portion-side expansion 74 of the base portion 71 are arranged on the center line L of the base portion 71. Also, the two base portion-side ribs 78 are connected to the central part of the base portion-side expansion 74 in the direction of air flow. As a result, similar effects to those of the eleventh embodiment are obtained.

Next, the fifteenth embodiment of the invention is explained with reference to FIG. 19. The fifteenth embodiment is different from the twelfth embodiment in the provision of second base portion-side ribs 78 a. The component parts similar to those of the twelfth embodiment are designated by the same reference numerals, respectively, and not described any more.

FIG. 19 is a perspective view showing the insert 7 according to the fifteenth embodiment. As shown in FIG. 19, the part of the base portion 71 not having the base portion-side ribs 78 is formed with the second base portion-side ribs 78 a projected outward along the direction in which the tubes 2 are stacked and extending in the direction substantially parallel to the length of the insert 7. According to this embodiment, the second base portion-side ribs 78 a have a substantially semicircular section.

Also, each of the second base portion-side ribs 78 a is arranged on one of the two sides of the base portion-side expansion 74. The two second base portion-side ribs 78 a are arranged on one and the other sides, respectively, of the center line L of the base portion 71. Also, on one and the other sides of the center line L of the base portion 71, the second base portion-side ribs 78 a are arranged in opposed relation with the base portion-side ribs 78, respectively, with respect to the base portion-side expansion 74.

As explained above, the part of the base portion 71 not having the base portion-side ribs 78 is formed with the second base portion-side ribs 78 a, thereby making it possible to further increase the stiffness of the insert 7 along the direction in which the tubes 2 are stacked. As a result, the pressure resistance and the quake resistance are further improved.

Also, by arranging each of the second base portion-side ribs 78 on each of the two sides of the base portion-side expansion 74, the second base portion-side ribs 78 a can be arranged over a wide range along the length of the insert 7. Further, the two second base portion-side ribs 78 a are arranged on one and the other sides of the center line L of the base portion 71, so that the second base portion-side ribs 78 can be arranged over a wide range of the insert 7 in the direction of air flow. Further, on one and the other sides of the center line L, the second base portion-side ribs 78 a are arranged in opposed relation with the base portion-side ribs 78, respectively, with respect to the base portion-side expansion 74, and therefore, the base portion-side ribs 78 or the second base portion-side ribs 78 a can be arranged substantially over the entire area of the base portion 71. As a result, the stiffness of the insert 7 along the direction in which the tubes 2 are stacked can be further increased, thereby improving the pressure resistance and the quake resistance further.

Next, the sixteenth embodiment of the invention is explained with reference to FIG. 20. The sixteenth embodiment is different from the fifteenth embodiment in that an end of each of the second base portion-side ribs 78 a is connected to the base portion-side expansion 74. The component parts similar to those of the fifteenth embodiment are designated by the same reference numerals, respectively, and not explained any more.

FIG. 20 is a perspective view showing the insert 7 according to the sixteenth embodiment. As shown in FIG. 20, the second base portion-side ribs 78 a each have an end thereof connected to the base portion-side expansion 74. According to this embodiment, the base portion-side ribs 78 and the second base portion-side ribs 78 a are aligned with each other on each of one and the other sides of the center line L. Also, the two second base portion-side ribs 78 a are connected one and the other ends, respectively, of the base portion-side expansion 74 in the direction of air flow.

As explained above, an end of each of the second base portion-side ribs 78 a is connected to the base portion-side expansion 74, and therefore, the stress concentration at the connector between the base portion 71 and the base portion-side expansion 74 is positively prevented.

Next, the seventeenth embodiment of the invention is explained with reference to FIG. 21. The component parts similar to those of the sixteenth embodiment are designated by the same reference numerals, respectively, and not explained again.

FIG. 21 is a perspective view showing the insert 7 according to the seventeenth embodiment of the invention. As shown in FIG. 21, the base portion-side ribs 78 and the second base portion-side ribs 78 a are connected to other than the ends of the base portion-side expansion 74 in the direction of air flow.

More specifically, the base portion-side ribs 78 and the second base portion-side ribs 78 a arranged upstream of the center line L of the base portion 71 in the air flow are connected to the part of the base portion-side expansion 74 upstream of the center line L in the air flow. Also, the base portion-side ribs 78 and the second base portion-side ribs 78 a arranged downstream of the center line L of the base portion 71 in the air flow are connected to the part of the base portion-side expansion 74 downstream of the center line L in the air flow. As a result, the effects similar to those of the sixteenth embodiment are achieved.

Next, the eighteenth embodiment of the invention is explained with reference to FIG. 22. The eighteenth embodiment is different from the fourteenth embodiment in the provision of the second base portion-side ribs 78 a. The component parts similar to those of the fourteenth embodiment are designated by the same reference numerals, respectively, and not explained again.

FIG. 22 is a plan view showing the insert 7 according to the eighteenth embodiment of the invention. As shown in FIG. 22, the part of the base portion 71 lacking the base portion-side ribs 78 is formed with the second portion-side ribs 78 a projected outward along the direction in which the tubes 2 are stacked and extending in the direction substantially parallel to the length of the insert 7. The second base portion-side ribs 78 a are each arranged on one of the two sides of the base portion-side expansion 74. The two base portion-side ribs 78 a are arranged on one and the other sides, respectively, of the center line L of the base portion 71.

According to this embodiment, the two base portion-side ribs 78 a are each connected to the other end (the side not connected with the base portion-side expansion 74) of the two base portion-side ribs 78, respectively. More specifically, the second base portion-side ribs 78 a arranged upstream of the center line L of the base portion 71 in the air flow are connected to the surface of the base portion-side ribs 78 upstream in the air flow. Also, the second base portion-side ribs 78 a arranged downstream of the center line L of the base portion 71 in the air flow are connected to the surface of the base portion-side ribs 78 a downstream in the air flow.

As explained above, the part of the base portion 71 not having the base portion-side ribs 78 has the second base portion-side ribs 78 a, respectively, and therefore, the stiffness of the insert 7 along the direction in which the tubes 2 are stacked is further improved. As a result, the pressure resistance and the quake resistance are improved.

Next, the nineteenth embodiment of the invention is explained with reference to FIGS. 23, 24. The component parts similar to those of the 5 th embodiment are designated by the same reference numerals, respectively, and not explained again.

FIG. 23 is a perspective view showing the insert 7 according to the nineteenth embodiment of the invention. As shown in FIG. 23, a first notch 76 is formed from one end to the other of the base portion 71 of the insert 7 at an angle to the direction of air flow. The first notch 76 is also formed continuously to the side ribs 72. Specifically, the tilt angle θ₁ of the part of the first notch 76 formed on the base portion 71 to the air flow is equal to the tilt angle θ₂ of the part of the first notch 76 formed on the side ribs 72 to the direction in which the tubes 2 are stacked. Also, the ends of the first notch 76 are arranged in the plane of a pair of the side ribs 72, respectively, and therefore, the side ribs 72 are not completely divided.

The pair of the side ribs 72 are formed with a second notch 79 inward from the outer end thereof along the direction in which the tubes 2 are stacked. The second notches 79 each have one end thereof open, and according to this embodiment, the other end (the end not open) of each of the second notches 79 is arranged in the plane of the side ribs 72. Also, the second notches 79 are each formed substantially in parallel to the first notch 76.

According to this embodiment, the second notch 79 formed on the side rib 72 downstream in the air flow (hereinafter referred to as the downstream-side second notch 79 b) along the length of the insert 7, as viewed from the first notch 76, is formed on the same side as the second notch 79 on the side rib 72 upstream in the air flow (hereinafter referred to as the upstream-side second notch 79 a). Specifically, the downstream-side second notch 79 b is arranged on the same side as the upstream-side second notch 79 a with respect to the first notch 76 in the direction along the length of the insert 7.

FIG. 24 is a plan view schematically showing the insert 7 before bending the side ribs 72 according to the nineteenth embodiment. As shown in FIG. 24, according to this embodiment, the first and second notches 76, 79 are formed at the same time that the insert 7 is press formed. The ends of the insert 7 with the first and second notches 76, 79 formed thereon along the short side thereof are bent in the same direction thereby to form the side ribs 72, thereby completing the insert 7 shown in FIG. 23.

As explained above, the first notch 76 is extended to the side ribs 72, and the ends of the first notch 76 are arranged in the plane of the pair of the side ribs 72, respectively. Thus, the side ribs 72 are not completely divided, and therefore, the unnecessary decrease of the stiffness of the insert 7 can be avoided. As a result, the pressure resistance and the quake resistance can be positively secured.

In view of the fact that the ends of the first notch 76 are arranged in the plane of the side rib pair 72, respectively, the stress generated along the length of the insert 7 is difficult to absorb. Therefore, the second notches 79 substantially in parallel to the first notch 76 are formed from the outer end of the side ribs 72 along the direction in which the tubes 2 are stacked. In this way, the stress along the length of the insert 7 can be easily absorbed. As a result, the thermal distortion can be further reduced.

Further, the first and second notches 76, 79 may be formed before press forming the insert 7. Thus, the process of forming the notches by cutting the insert 7 is not required after forming the core 4 by brazing the insert 7 together with the tubes 2 and the fins 3. As a result, the formability is improved.

Next, the twentieth embodiment of the invention is explained with reference to FIG. 25. The twentieth embodiment is different from the nineteenth embodiment in that the other end of each of the second notches 79 of the insert 7 is arranged at a different position. The component parts similar to those of the nineteenth embodiment are designated by the same reference numerals, respectively, and not explained more.

FIG. 25 is a perspective view showing the insert 7 according to the twentieth embodiment. As shown in FIG. 25, the other end (the end not open) of each second notch 79 is arranged in the plane of the base portion 71 of the insert 7. As a result, the effects similar to those of the nineteenth embodiment are achieved.

Next, the twenty-first embodiment of the invention is explained with reference to FIG. 26. The twenty-first embodiment is different from the twentieth embodiment in that the second notches 79 are arranged at different positions. The component parts similar to those of the twentieth embodiment are designated by the same reference numerals, respectively, and not explained more.

FIG. 26 is a perspective view showing the insert 7 according to the twenty-first embodiment. As shown in FIG. 26, the downstream-side second notch 79 b is arranged on the side of the first notch 76 far from the upstream-side second notch 79 a along the length of the insert 7. Specifically, the downstream-side second notch 79 b is arranged on the other side of the first notch 76 far from the upstream-side notch 79 a in the longitudinal direction of the insert 7. As a result, the effects similar to those of the twentieth embodiment are achieved.

Next, the twenty-second embodiment of the invention is explained with reference to FIG. 27. The twenty-second embodiment is different from the twenty-first embodiment in the provision of third notches 80. The component parts similar to those of the twenty-first embodiment are designated by the same reference numerals, respectively, and not explained more.

FIG. 27 is a perspective view showing the insert 7 according to the twenty-second embodiment. As shown in FIG. 27, a pair of side ribs 72 are each formed with the third notch 80 inward from the outer end along the direction in which the tubes 2 are stacked. The third notches 80 each have only one end thereof open, and according to this embodiment, the other end (the end not opened) of each of the third notches 80 is arranged in the plane of the side ribs 72. Also, the third notches 80 are formed substantially in parallel to the first and second notches 76, 79.

According to this embodiment, the third notch 80 formed on the side rib 72 upstream in the air flow (hereinafter referred to as the upstream-side third notch 80a) is arranged on the side of the upstream-side second notch 79 a far from the first notch 76. Also, the third notch 80 formed on the side rib 72 downstream in the air flow (hereinafter referred to as the downstream-side third notch 80 b) is arranged on the side of the first notch 76 far from the downstream-side second notch 79 b. The third notches 80 are also formed at the same time that the insert 7 is press formed.

As explained above, the insert 7 is formed with the second and third notches 79, 80 substantially in parallel to the first notch 76 from the outer end of the side ribs 72 along the direction in which the tubes 2 are stacked. Thus, the stress generated along the length of the insert 7 can be absorbed more easily. As a result, the thermal distortion can be further reduced.

Finally, other embodiments will be described. Although the embodiments described above are an application of the invention to the cross-flow radiator in which the cooling water flows in horizontal direction. Nevertheless, this invention is applicable also to the down-flow radiator in which the cooling water flows vertically.

Also, this invention is not limited to the embodiments described above in which the stress absorber, of the insert 7, is not in contact with the core portion 4. As an alternative, the stress absorber of the insert 7 may be in contact with the core portion 4.

Further, unlike in the seventh and eighth embodiments described above in which three notches 76 are formed in the base portion 71, two or four or more notches 76 may be formed.

In similar fashion, in spite of the fact that the base portion 71 is formed with four notches 76 according to the ninth embodiment, two or three or not less than five notches may be formed with equal effect.

The base portion-side ribs 78, though formed with a substantially semicircular section according to the eleventh to eighteenth embodiments, may alternatively have the section of other shapes such as triangle or rectangle.

In similar fashion, according to the fifteenth to eighteenth embodiments described above, the second base portion-side ribs 78 a are formed to have a substantially semicircular section. Nevertheless, the section may be in any of other shapes including a triangle and a rectangle.

While the invention has been described by reference to specific embodiments chosen for purposes of illustration, it should be apparent that numerous modifications could be made thereto, by those skilled in the art, without departing from the basic concept and scope of the invention. 

1. A heat exchanger comprising: a core portion including a plurality of tubes with a heat medium flowing therein; a pair of header tanks extending in a direction perpendicular to the length of the tubes at the longitudinal ends of the tubes and communicating with the tubes; and a pair of inserts arranged substantially parallel to the length of the tubes, and in such a manner as to contact the core portion at the ends of the core portion to transfer the heat from the core portion, and having the ends thereof supported on the header tanks; wherein a stress absorber to absorb the stress generated along the length of each insert is formed in the insert; wherein the stress absorber is formed over each insert from the upstream side to the downstream side in the air flow; and. wherein the stress absorber is arranged in such a manner that the most upstream end and the most downstream end thereof in the air flow are not superposed, one on the other, along the direction of air flow.
 2. A heat exchanger according to claim 1, wherein each insert includes a base portion having a surface substantially parallel to the flat surfaces of the tubes and extending substantially parallel to the length of the tubes, and a pair of ribs are projected in a direction substantially perpendicular to the base portion from the ends of the base portion in the direction of air flow and are extended substantially parallel to the length of the tubes; wherein the portions of the ribs corresponding to the most upstream end and the most downstream end of the stress absorber are formed with notches, respectively; and wherein each stress absorber constitutes a base portion-side expansion of the base portion having a substantially U-shaped cross section.
 3. A heat exchanger according to claim 2, wherein the base portion-side expansion is formed diagonally with respect to the direction of air flow.
 4. A heat exchanger according to claim 2, wherein the base portion-side expansion is split into a plurality of parts in the direction of air flow, and wherein the plurality of the base portion-side expansions are coupled to each other through slits formed in the base portion.
 5. A heat exchanger according to claim 4, wherein the plurality of the base portion-side expansions are not arranged in alignment.
 6. A heat exchanger according to claim 4, wherein the plurality of the base portion-side expansions are tilted in different directions with respect to the direction of air flow.
 7. A heat exchanger according to claim 4, wherein the plurality of the base portion-side expansions are arranged substantially parallel to the direction of air flow in such a manner as not to be superposed, one on another, in the direction of air flow.
 8. A heat exchanger according to claim 1, wherein the tubes each have a flat cross section in the direction of air flow, and wherein each insert includes a base portion having a surface substantially parallel to the flat surface of the tubes and extending in the direction substantially parallel to the length of the tubes and a pair of ribs projected in the direction substantially perpendicular to the base portion and extending in the direction substantially parallel to the length of the tubes, and wherein the stress absorber is a notch cut in the base portion diagonally to the direction of air flow.
 9. A heat exchanger according to claim 8, wherein only one end of the notch is open.
 10. A heat exchanger according to claim 8, comprising a plurality of notches.
 11. A heat exchanger according to claim 8, comprising a plurality of notches each having only one open end; wherein the open ends of the plurality of the notches are arranged on the base portion and alternate between the upstream side and the downstream side in the air flow.
 12. A heat exchanger according to claim 10, wherein the plurality of the notches are tilted in different directions with respect to the direction of air flow.
 13. A heat exchanger according to claim 8, wherein the notch is formed in the base portion, the portion of each of the pair of the ribs adjoining the corresponding notch is formed with a U-shaped rib-side expansion in the direction of air flow, and each stress absorber includes the corresponding rib-side expansion.
 14. A heat exchanger according to claim 1, wherein the insert (7) is formed with protrusions (78) projected outward thereof along the direction in which the tubes (2) are stacked, and wherein the protrusions (78) are connected to a stress absorber (74, 76, 77).
 15. A heat exchanger according to claim 1, wherein the tubes (2) have a flat section along the direction of air flow, wherein the insert (7) includes a base portion (71) having a surface substantially parallel to the flat surface of the tubes (2) and extending in the direction substantially parallel to the length of the tubes (2), wherein the base portion (71) has base portion-side ribs (78) projected outward along the direction in which the tubes (2) are stacked and extending in the direction substantially parallel to the length of the insert (7), wherein the stress absorber is a base portion-side expansion (74) having the section expanded substantially in the shape of U, and wherein an end of each of the base portion-side ribs (78) is connected to the base portion-side expansion (74).
 16. A heat exchanger according to claim 15, wherein the insert (7) has a pair of side ribs (72) projected in the direction substantially perpendicular to the base portion (71) from the ends of the base portion (71) along the direction of air flow, and wherein the portions of the side ribs (72) corresponding to the most upstream end and the most downstream end of the base portion-side expansion (74) are formed with notches (73 a, 73 b), respectively.
 17. A heat exchanger according to claim 15, wherein the base portion-side ribs (78) are formed on both sides, respectively, of the base portion-side expansion (74).
 18. A heat exchanger according to claim 17, wherein the base portion-side ribs (78) are arranged on one and the other sides, respectively, of the center line (L) of the base portion (71) across the length of the insert (7) in the air flow.
 19. A heat exchanger according to claim 15, wherein the base portion-side ribs (78) are formed on both sides, respectively, of the base portion-side expansion (74) and also on the center line (L) of the base portion (71) across the length of the insert (7) in the air flow.
 20. A heat exchanger according to claim 15, wherein the base portion (71) is formed with second base portion-side ribs (78 a) projected outward along the direction in which the tubes (2) are stacked and extending in the direction substantially parallel to the length of the insert (7).
 21. A heat exchanger according to claim 18, wherein the base portion (71) is formed with second base portion-side ribs (78 a) projected outward along the direction in which the tubes (2) are stacked and extending in the direction substantially parallel to the length of the insert (7), wherein the base portion-side ribs (78) are formed on both sides, respectively, of the base portion-side expansion (74) and arranged on one and the other sides, respectively, of the center line (L) of the base portion (71) across the length of the insert (7) in the air flow, and wherein the second base portion-side ribs (78 a) are arranged in opposed relation to the base portion-side ribs (78), respectively, with respect to the base portion-side expansion (74) on each of one and the other sides of the center line (L).
 22. A heat exchanger according to claim 21, wherein the second base portion-side ribs (78 a) each have an end thereof connected to the base portion-side expansion (74).
 23. A heat exchanger according to claim 15, wherein the base portion-side ribs (78) are aligned on both sides, respectively, of the base portion-side expansion (74), wherein the base portion (71) is formed with second base portion-side ribs (78 a) projected outward along the direction in which the tubes (2) are stacked and extending in the direction substantially parallel to the length of the insert (7), and wherein the second base portion-side ribs (78 a) are arranged on one and the other sides, respectively, of the base portion-side expansion (74) and connected to the base portion-side ribs (78).
 24. A heat exchanger according to claim 8, wherein the notch (76) extends to the side ribs (72), wherein the ends of the notch (76) are arranged in the plane of the pair of the side ribs (72), respectively, wherein the insert (7) is formed with second notches (79) substantially in parallel to the notch (76) from the outer end of the side ribs (72) along the direction in which the tubes (2) are stacked, and wherein the second notches (79) each have only one end thereof open. 